RE: Ltr to NucNews

[Tom Morgan <tmorgan@ISOTOPEPRODUCTS.COM>]

Statistical analysis of small populations can be very difficult.  The more

variables one adds to the equation, the larger the sample population has to

be to detect a statistically significant difference.



I have not read the study(ies) in question, but from my experience I would

guess that they attempted to account for dose, length of exposure, age and

smoking status.  Such a study would require hundreds, if not thousands, of

participants before it had the statistical power to detect a significant

difference between two populations.  The required size of the population can

increase rapidly (even geometrically) as the differences get smaller and/or

the number of variables increases.



"There are lies, damn lies and statistics" (Mark Twain, I believe)



Thomas L. Morgan, Ph.D.

Director, Health Physics

Radiation Safety Officer

Isotope Products Laboratories

24937 Avenue Tibbitts

Santa Clarita, CA 91355

661-257-8300 x215

818-558-4087 (fax)





-----Original Message-----

From: Susan Gawarecki [mailto:loc@ICX.NET]

Sent: Tuesday, July 10, 2001 8:07 PM

To: RADSAFE; tedrock@CPCUG.ORG

Subject: Re: Ltr to NucNews





Don't forget the combined female nuclear facilities workers study, using

data comparing badged and unbadged women who worked at 10 different DOE

facilities.  Because the women who had low levels of exposure were

heathier than those with no exposure (unbadged), the researcher

concluded there must be an internal "healthy worker" effect -- only

healthy women chose to work in areas with radiological exposure.  Note

that the design of this study was supposed to account for that

confounding (or is it confounded?) healthy worker effect because ALL

particants were workers!



When I asked if this could show a possible positive effect of exposure

to radiation, he said it couldn't.  I'm not an epidemiologisist, so can

someone enlighten me as to how such a study design could show a harmful

effect of radiation exposure but not a positive one?  



My own opinion only,



Susan Gawarecki



Ted Rockwell wrote:

<snip>

> Isn't

> that why DOE did the ten-year multimillion dollar Nuclear Shipyard Workers

> Study, with individually-badged workers compared with other,

non-irradiated,

> shipyard workers in similar trades?  And shouldn't we also use the 10,000

> apartment dwellers in Taiwan who were unwittingly exposed for nearly 20

> years by Co-60 contaminated rebar (maximum dose about one Sievert during

the

> first year) ?  And the many excellent studies of populations in locations

of

> high natural radiation?  And how about the radium dial painters, whose

> individual radium body burdens are well known?

> 

> But these situations all gave "wrong answers."  They showed, as predicted

> from biology, that low-dose radiation stimulates the body's defenses and

> actually reduces cancer mortality by a highly significant amount.

<snip>

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